8abe
Complex III2 from Yarrowia lipolytica, oxidised with ferricyanide, b-position
Structural highlights
FunctionQCR2_YARLI Component of the ubiquinol-cytochrome c oxidoreductase, a multisubunit transmembrane complex that is part of the mitochondrial electron transport chain which drives oxidative phosphorylation. The respiratory chain contains 3 multisubunit complexes succinate dehydrogenase (complex II, CII), ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate to transfer electrons derived from NADH and succinate to molecular oxygen, creating an electrochemical gradient over the inner membrane that drives transmembrane transport and the ATP synthase. The cytochrome b-c1 complex catalyzes electron transfer from ubiquinol to cytochrome c, linking this redox reaction to translocation of protons across the mitochondrial inner membrane, with protons being carried across the membrane as hydrogens on the quinol. In the process called Q cycle, 2 protons are consumed from the matrix, 4 protons are released into the intermembrane space and 2 electrons are passed to cytochrome c.[UniProtKB:P07257] Publication Abstract from PubMedMovement of the Rieske domain of the iron-sulfur protein is essential for intramolecular electron transfer within complex III(2) (CIII(2)) of the respiratory chain as it bridges a gap in the cofactor chain towards the electron acceptor cytochrome c. We present cryo-EM structures of CIII(2) from Yarrowia lipolytica at resolutions up to 2.0 A under different conditions, with different redox states of the cofactors of the high-potential chain. All possible permutations of three primary positions were observed, indicating that the two halves of the dimeric complex act independently. Addition of the substrate analogue decylubiquinone to CIII(2) with a reduced high-potential chain increased the occupancy of the Q(o) site. The extent of Rieske domain interactions through hydrogen bonds to the cytochrome b and cytochrome c(1) subunits varied depending on the redox state and substrate. In the absence of quinols, the reduced Rieske domain interacted more closely with cytochrome b and cytochrome c(1) than in the oxidized state. Upon addition of the inhibitor antimycin A, the heterogeneity of the cd(1)-helix and ef-loop increased, which may be indicative of a long-range effect on the Rieske domain. Analysis of the conformational heterogeneity of the Rieske iron-sulfur protein in complex III(2) by cryo-EM.,Wieferig JP, Kuhlbrandt W IUCrJ. 2023 Jan 1;10(Pt 1):27-37. doi: 10.1107/S2052252522010570. PMID:36598500[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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